This invention relates to sampling devices for obtaining samples of body fluids such as sweat, tears and saliva for subsequent analysis, and to methods of using these devices in preparing samples for analysis.
There has been a growing interest in recent years in the nonintrusive clinical sampling of body fluids for detecting various chemical substances. This is largely the result of improved analytical techniques and the realization that many of the components of physiological interest (metabolites, drugs, etc.) contained in blood samples obtained by intrusive means (e.g. venipuncture or finger and heel sticks) are also contained in other body fluids such as sweat, tears and saliva, which can be obtained much more easily and at reduced risk. In addition, these samples may be advantageous for testing for components of physiological interest.
This latter advantage may be illustrated by comparing the utility of urine and saliva samples to establish recent marijuana usage. Since marijuana can be detected in urine for up to 40 days after the last use of the drug, while saliva will only show evidence of such usage within the last 48 hours, saliva samples are much more useful than urine samples for detecting recent use of the drug.
Body fluid sampling and testing usually involves four steps, viz.:
1. sample collection, PA1 2. extraction of the sample from the collection media, PA1 3. reaction of the sample with analytical reagents, and PA1 4. detection and/or measurement of physiologically active contents.
In the past, the nonintrusive collection of body fluid samples has commonly been accomplished by the use of devices such as cotton swabs, absorbent papers and pads, which are used to absorb fluid samples. Once collected, these devices are placed in a vessel in which the sample is extracted into a suitable solvent by means of diffusion, with or without mechanical agitation. Sample extraction by means of unassisted diffusion is quite slow, usually requiring several minutes. If this process is speeded up with agitation, extraneous material such as cotton or paper fibers may be entrained in the extraction fluid along with the sample and may have to be removed prior to the reagent reaction of step 3 above.
Various prior patents disclose different types of samplers and techniques for obtaining and preparing samples for spectral or spot analyses. For example, U.S. Pat. No. 3,452,601 and No. 3,511,570 to Mogayzel et al. disclose the arrangement and use of a device, for obtaining a liquid sample for subsequent spectroscopic analysis, which comprises an elongated porous mass enclosed at least partially by a non-porous tubular member or shield. The sample is obtained by bringing one end of the mass into contact with a solute containing the material to be analyzed. The porous mass acts as a wick and picks up the solute through capillary action. Part of the porous mass containing the sample is removed, crushed, dried and analyzed. In a modification described in U.S. Pat. No. 3,496,777 to Packer et al., a device for preparing samples for spectroscopic analysis is formed of an elongated porous wick enclosed on its sides to prevent evaporation but open at the ends, with a separate porous pointed tip of porous, spectroscopic-grade matrix material removably placed against one end of the wick. The sample, absorbed through the other end of the wick, collects in the tip, which is then removed and crushed for analysis.
U.S. Pat. No. 3,326,205 to Lewis discloses an implement for removing a liquid with a tube while preventing other (particulate) matter from being drawn into the tube. In this device, the tube through which the liquid is removed terminates in a hollow spoon-like collecting member having two co-extensive, connected walls, one wall being smooth and imperforate while the other is perforated or in the form of a mesh or screen.
U.S. Pat. No. 4,334,879 to Fujimori discloses an applicator comprising a holder and an applicator blade of porous, absorbent material formed as a rectangular plate and mounted at the end of the holder. The blade is dipped into a liquid in order to absorb a quantity of the liquid, and is then pushed onto an electrically energizable film to express a fine, uniform sample of liquid onto the film.
U.S. Pat. No. 4,190,060 to Greenleaf et al. describes a sweat collection capsule comprising a frame held on the skin, a closure secured to the frame, and an absorbent material removably mounted next to the skin in a cavity formed by the frame and the closure.
U.S. Pat. No. 3,368,549 to Barr et al. relates to a swab-like structure comprising a support and a culture medium-carrying means on an end portion of the support, with a sterile container provided for removably housing the support.